3CCFE575BT-D Not Detected

I am running Red Hat 6.0 on a Toshiba 480CDT. Untill recently I have been successfully using a 3C589 (I think) PCMCIA Ethernet card. I have recently swapped to a 3C575 (3CCFE575BT-D). The card is not detected at startup, or if I insert or remove the card whilst running. There are no associated messages in the system log and cardinfo shows both sockets to be empty. cardmgr still successfully detects my Hayes modem, and the 3C575 works OK with Windows 95.

I'm quite expecting to make config changes, but at the moment the 3C575 isn't even recognised as an unsupported card.